Unidentified Floating Object

Alien spaceship with tentacles attached?

Upside-down nuclear explosion? With tentacles attached?

Or is it our old friend Porpita porpita? The Blue Button.

Or maybe it's a child's rendition of an alien sun. With tentacles attached.

Nah. It's a Blue Button. They're those floating colonies of polyps...

Starting life as tiny medusae, basically jellyfish, like many other members of the phylum cnidaria. Each colony develops from one, tiny bag-of-mostly-water with big dreams.

They soon develop their float. It's quite tough because it's made of chitin, the same stuff as insect exoskeletons, and it's riddled with air-filled chambers. It gets to about 2.5 cm (an inch) across, so it's a really small spaceship.

Hanging from the underside of the float are concentric circles of dactylozooids. These are the polyps responsible for catching food and defending the colony.

Each dactylozooid is covered in little bulbs on stalks. The stinging cells are in these bulbs.

The stings aren't dangerous to humans, but it's a gauntlet of near certain death for the tiny prey of Porpita.

The polyps can also be retracted in a sort of spinning motion when the Blue Button is disturbed, at which point it looks like an upside down gas fire. With tentacles, naturally.

It all looks rather lovely...

Until you take a closer look at the underside.

Those beautiful, blue tentacles are only on the outer edge...

They surround the gastro-gonozooids, which are the polyps responsible for reproduction and actually digesting the food caught by the dactylozooids.

It's a disgusting mass of tentacles that really ought to be hidden away in a bag, like we do with our intestines.

And at its centre...

Lies the central gastrozooid, the King of Mouths.

Soon enough, the gastro-gonozooids produce medusae of their own.

Right from the start they have within their tissues the tiny, symbiotic algae that will provide them energy from the sun throughout their life.

One day they'll become a wondrous star of their very own, with a nasty, fleshy underbelly. "The bigger the front, the bigger the back" as Freud almost said.

Images: Alvaro E. Migotto, Cifonauta